The quest for higher processor performance and the advent of high-density information technology (IT) equipment, such as blade servers, have posed a critical problem as to increases in power consumption of IT systems. As a solution to this problem, the development of power consumption reduction technologies is advanced, such as low power consumption processors and high efficiency cooling methods. Unfortunately, per-apparatus power-saving techniques have limits. Thus, in order to obtain more significant power-saving effects, a need is felt to make efforts for achieving an adequate approach on the system level.
Especially, in view of the fact that servers consume a certain amount of electric power due to the flow of a leakage current therein even when these are set to zero (0) in working rate thereof, a system condition with the use of a great number of servers of low working rates is inferior in efficiency in terms of the electric power. Thus, it is expected to achieve power-saved system operation/management which uses a minimal number of servers at the highest possible operation rate while forcing the power supply of an unused server(s) to turn off. In contrast, a virtualized server is movable or transferable to another physical server; so, when a certain kind of business task decreases in load, virtual servers which are being executed by a low operation-rate server are gathered together for concentrative aggregation in such a way as to reduce the number of presently operating physical servers, thereby making it possible to save power to be consumed by an entire system. As such virtual servers become widely used in practical applications, the above-stated power-saved system operation/management is becoming reality.
However, when an attempt is made to operate only a few number of servers in a heavily-loaded state while letting the others be shut down, the surrounding area of each such active server becomes a heat accumulation space of high temperatures-say, hot spot. When an entire cooling output is increased in order to cool down spatially scattered hot spots, electric power needed for this cooling operation can excessively increase beyond an acceptable level. In this respect, a method for determining a to-be-activated server by taking into consideration a heat distribution is disclosed in US2003/0177406A1. A method of optimizing a server configuration by taking account of the cooling ability or “coolability” of a built-in cooling apparatus of a server is disclosed in JP-A-2004-126968.